Method and apparatus for cleaning/drying hydrophobic wafers

ABSTRACT

A method and an apparatus that uses a surfactant to clean a hydrophobic wafer is provided. In a first aspect, the method may clean and dry a wafer without applying pure DI water to the wafer. In a second aspect, the method may clean a wafer by applying pure DI water to the wafer only for a short duration of time such that the DI water application ceases prior to or as soon as a surfactant solution is rinsed from the wafer thereafter the wafer is dried. In a further aspect a hydrophobic wafer is maintained wetted with surfactant as it is transferred between cleaning apparatuses and is rinsed via diluted surfactant or via a brief DI water spray and is thereafter dried.

[0001] This application is a divisional of U.S. patent application Ser.No. 09/644,177, filed Aug. 23, 2000, which claims priority from U.S.Provisional Patent Application Serial No. 60/150,656, filed Aug. 25,1999, both of which are hereby incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to apparatuses andmethods for cleaning thin discs, such as semiconductor wafers, compactdiscs, glass substrates and the like. More specifically, the presentinvention relates to cleaning hydrophobic wafers using a surfactantcontaining solution.

BACKGROUND OF THE INVENTION

[0003] As semiconductor device geometries continue to decrease, theimportance of ultra clean processing increases. Conventional wafercleaning and drying methods include one or more rinsing steps eitherwith pure deionized water or with a cleaning solution. Before cleaning,the surfaces of silicon wafers typically are converted from hydrophobicto hydrophilic because hydrophilic surfaces do not attract particles andhydrophilic surfaces help rinsing water and cleaning solution to wet thewafer's surfaces.

[0004] Conversion from a hydrophobic state to a hydrophilic state occursfor example when the surfaces of silicon wafers react with oxygen or anoxidizer to form a thin oxide layer, which passivates the surfaces ofthe silicon wafer (i.e., forms a passivation layer). The passivationlayer is hydrophilic, and thus facilitates subsequent cleaningprocesses. The surfaces of low-k dielectric wafers (wafers that have alow-k dielectric formed thereon), however, do not react with oxygen oran oxidizer to form a hydrophilic passivation layer. Thus, absenttreatment, low-k dielectric wafers have hydrophobic surfaces. Therefore,when aqueous cleaning solutions are applied to the surfaces of a low-kdielectric wafer, the aqueous cleaning solutions are repelled therefrom.

[0005] Hydrophobic wafers are more difficult to clean than hydrophilicsilicon wafers, due to the poor wettability of aqueous cleaningsolutions on hydrophobic low-k dielectric wafers. Also, the efficiencyof chemical residues removal by deionized water rinsing is very low.Drying of hydrophobic wafers is even more challenging than cleaning, dueto the high affinity of particle contaminants to the hydrophobicsurfaces. Further, because pure DI water is typically sprayed directlyonto the hydrophobic surfaces during rinsing, water marks or residuesare commonly observed on the hydrophobic surfaces during drying. Suchwater marks and residue may cause subsequent device failure. Thesemiconductor industry is increasing the use of low-k dielectric wafersand, hence, much attention has been directed to improved methods forcleaning a hydrophobic wafer.

[0006] Accordingly, a need exists for an improved method and apparatusfor cleaning hydrophobic wafers.

SUMMARY OF THE INVENTION

[0007] The present invention provides a method and an apparatus thatuses a surfactant to clean a hydrophobic wafer. The inventive cleaningmethod comprises two main aspects. In the first aspect, the inventivecleaning method may clean a wafer by applying a surfactant without usingpure DI water. In the second aspect, the inventive cleaning method mayclean a wafer by applying a surfactant followed by applying pure DIwater during a short rinsing step that is sufficiently short so thatrinsing ceases in one aspect, before the surfactant has been completelyrinsed from the wafer, thus eliminating or minimizing the contact ofpure DI water with the wafer. These aspects may be performed in anyconventional cleaning and drying apparatus that is appropriatelyprogrammed to perform the inventive method. For example, the inventivemethods may be employed within an SRD, scrubber, or within any tank orother type system that includes spray nozzles, any of which may furtherinclude application of vapors to achieve Marangoni drying. In a thirdaspect of the invention, either of the methods described above isperformed as a final step in a cleaning sequence that employs aplurality of cleaning apparatuses, and that further maintains asurfactant layer on the wafer during transfer between the plurality ofcleaning apparatuses, and that does not contact the wafer with pure DIwater prior to the final clean/dry step, if at all.

[0008] Other features and aspects of the present invention will becomemore fully apparent from the following detailed description of thepreferred embodiments, the appended claims and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a flowchart of an inventive cleaning method that may beperformed in any apparatus that may clean and dry a hydrophobic wafer;

[0010]FIG. 2 is a side cross-sectional view of an SRD that may performthe inventive cleaning method;

[0011]FIG. 3 is a side elevational view of an IPA dryer with a tankmodule that may rinse and dry a hydrophobic wafer using the inventivecleaning method;

[0012]FIG. 4A is a partially sectional side view of an inventive IPAdryer with an SRD chamber that may rinse and dry a hydrophobic waferusing the inventive cleaning method;

[0013]FIG. 4B is a top plan view of the IPA dryer of FIG. 4A;

[0014]FIG. 5 is a side view of a scrubber that may perform the inventivecleaning method;

[0015]FIG. 6 is a flowchart of an inventive cleaning method that may beperformed in a cleaning sequence that employs a plurality of cleaningapparatuses; and

[0016]FIG. 7 is a schematic side elevational view of a cleaner that mayemploy the inventive cleaning method of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An inventive cleaning method and apparatus that uses a surfactantto clean hydrophobic wafers (e.g., low-k dielectric wafers) is provided.FIG. 1 is a flowchart useful in describing two aspects of an inventivecleaning method 11 that may be performed in any apparatus that may cleanand dry a wafer. Such apparatuses include, for example, aspin-rinse-dryer (SRD) as described further below with reference to FIG.2, an IPA dryer that employs a fluid tank as described further belowwith reference to FIG. 3, an IPA dryer that employs an SRD chamber asdescribed further below with reference to FIGS. 4A-B, a scrubber deviceas described further below with reference to FIG. 5, or any conventionaldryer that may rinse and dry a wafer. Further aspects of the inventivecleaning method may be performed in a cleaning sequence that employs aplurality of cleaning apparatuses as described below with reference tothe flow chart of FIG. 6, and the cleaning system of FIG. 7.

[0018] With reference to FIG. 1, the inventive cleaning method 11 startsat step 13. In step 15, a cleaning solution that comprises a surfactant(i.e., a surfactant containing solution) is applied to the surfaces of ahydrophobic wafer in an apparatus that may clean and dry the hydrophobicwafer, thus forming a layer of surfactant containing solution on thewafer. In one aspect, the surfactant containing solution may comprise aWAKO NCW surfactant (e.g., NCW-601A: an aqueous solution (approximately30 percent) of polyoxyalkylene alkylphenyl ether, NCW-1001:polyoxyalkylene alkyl ether 30 percent (w/w) aqueous solution, NCW-1002:polyoxyalkylene alky ether 10 percent (w/w) aqueous solution). The WAKONCW surfactant may have a concentration of 0.01% to 0.1% by volume.

[0019] In a first aspect the process proceeds to step 17. In step 17,pure DI water is applied to the layer of surfactant containing solutionformed on the surfaces of the hydrophobic wafer. The pure DI water isapplied for a sufficiently short period of time (e.g., approximatingfive seconds or less) such that as the layer of surfactant containingsolution is removed (step 19 a) or nearly removed (step 19 b), the pureDI water spray stops. Accordingly, DI water is not applied directly tothe hydrophobic wafer's surface. Thus, fewer water marks may form on thesurfaces of the hydrophobic wafer as the wafer is dried (step 21).Thereafter the process ends at step 23.

[0020] In a second aspect the process proceeds from step 15 to step 25.In step 25, a diluted surfactant containing solution that is more dilutethan the surfactant containing solution used in step 15 is applied tothe layer of surfactant containing solution formed on the surfaces ofthe hydrophobic wafer. In one aspect, the diluted surfactant containingsolution is applied for ten seconds or less, depending on thehydrophobicity of the wafer. In the second aspect, because pure DI wateris never used (only diluted surfactant containing solution is used torinse the hydrophobic wafer), water marks may not form on the surfacesthereof as the wafer is dried (step 21). Thereafter, the process ends atstep 23. For test results that employed a diluted NCW surfactant, havinga concentration of less than 500 parts per million (ppm), no particleresidue issue resulted. Accordingly, for wafers with higherhydrophobicity a cleaning solution of, for example, 1000 ppm may berinsed with a more dilute cleaning solution having 500 ppm.

[0021]FIG. 2 is a side cross-sectional view of an SRD 101 that mayperform the inventive cleaning method 11 of FIG. 1. Within the SRD 101,a hydrophobic wafer W is shown supported by a pair of grippers G, whichextend from a rotateable flywheel 105. The flywheel 105 is coupled to amotor 107 adapted to control the rotational speed of the flywheel 105.

[0022] A pair of nozzles 109 a, 109 b are coupled to a source ofsurfactant containing solution 111 and a source of rinsing fluid 112,and are positioned to supply the surfactant containing solution and therinsing fluid to the center of the front and back surfaces of thehydrophobic wafer W, respectively. In the first aspect, the rinsingfluid may comprise pure DI water. In the second aspect, the source ofrinsing fluid 112 may comprise a diluted surfactant containing solutionthat is more dilute than the surfactant containing solution that iscontained in the source of surfactant containing solution 111.

[0023] A controller 113 is coupled to the source of surfactantcontaining solution and the source of rinsing fluid 111, and comprises amemory having a program stored therein adapted to automatically performthe inventive cleaning method of FIG. 1. The SRD may be configured asdescribed in U.S. patent application Ser. No. 09/544,660, filed Apr. 6,2000 (AMAT No. 3437/CMP/RKK) the entire disclosure of which isincorporated herein by this reference.

[0024] The operation of both aspects of the SRD 101 are described below.Regarding the first aspect, in operation, the nozzles 109 a, 109 bsupply the surfactant containing solution to the surface of thehydrophobic wafer W as the flywheel 105 rotates, thus forming a layer ofsurfactant containing solution across the surface of the wafer.Thereafter, the surfactant solution spray ceases and the flywheel 105continues to rotate while the nozzles 109 a, 109 b supply pure DI waterto the layer of surfactant containing solution formed on the front andback surfaces of the hydrophobic wafer W. The DI water is supplied for ashort period of time (e.g., approximately five seconds or less).

[0025] When the layer of surfactant containing solution formed on thehydrophobic wafer's surface is removed or nearly removed, the nozzles109 a, 109 b shut off and the motor 107 either maintains or increasesthe rotational speed (e.g., to approximately 1000 to 2500 rpm) of theflywheel 105 such that any remaining DI water and surfactant containingsolution are displaced from the hydrophobic wafer W via the rotationalspeed, and/or dried from the hydrophobic wafer W. Optionally, heatednitrogen also may be directed to the hydrophobic wafer W's surfaces viaa nozzle (not shown) to further aid in drying the hydrophobic wafer W.

[0026] In the first aspect, because pure DI water is applied only to thelayer of surfactant containing solution on the hydrophobic wafer W'ssurface, and is not applied directly to the hydrophobic wafer W'ssurface, fewer water marks may form on the surfaces of the hydrophobicwafer W.

[0027] The operation of the second aspect may comprise the same steps asthe operation of the first aspect. In the second aspect, however, thenozzles 109 a, 109 b supply a diluted surfactant containing solution tothe layer of surfactant containing solution formed on the front and theback surfaces of the hydrophobic wafer W thereby reducing theconcentration of surfactant formed on the surface of the wafer W. In oneaspect, depending on the hydrophobicity of the wafer, the dilutedsurfactant containing solution is applied for ten seconds or less.

[0028] In the second aspect, because pure DI water is never used, andonly diluted surfactant containing solution is used to rinse thehydrophobic wafer W, fewer water marks may form on the surface of thewafer W.

[0029] Inventive IPA dryers that may rinse and dry a hydrophobic waferusing the inventive cleaning method are described below with referenceto FIG. 3, which shows a tank module configured for Marangoni drying,and with reference to FIGS. 4A-B, which show an SRD configured forMarangoni drying.

[0030]FIG. 3 is a side elevational view of an IPA dryer 201 that employsa tank 203 and that may rinse and dry a hydrophobic wafer using theinventive cleaning method. The tank 203 is filled with a surfactantcontaining solution. The IPA dryer 201 comprises a lifting mechanism 205coupled to the tank 203 and adapted to lift wafers from the tank 203. Arinsing fluid supply comprising one or more rinsing fluid nozzles 207 ispositioned to spray rinsing fluid across the entire horizontal diameterof a hydrophobic wafer W as the hydrophobic wafer W is lifted from thetank 203, and a drying vapor supply comprising one or more drying vapornozzles 211 is positioned to flow drying vapor (e.g., IPA) across theentire horizontal diameter of the hydrophobic wafer W as the hydrophobicwafer W is lifted from the tank 203. optionally, a wafer shuttle 213 maybe positioned to transfer the hydrophobic wafer W to the liftingmechanism 205.

[0031] A first pair of rails 215 may be permanently mounted within thetank 203 and may be positioned to support the hydrophobic wafer W as thelifting mechanism 205 lifts the hydrophobic wafer W. A second pair ofrails 217 may be permanently mounted above the tank 203 and may bepositioned to receive the hydrophobic wafer W from the first pair ofrails 215.

[0032] In a first aspect, the rinsing fluid may comprise pure DI water.In a second aspect, the rinsing fluid may comprise a diluted surfactantcontaining solution that is more dilute than the surfactant containingsolution in the tank 203.

[0033] The rinsing fluid nozzles 207 are coupled to a controller 219,and the controller 219 comprises a memory having a program storedtherein adapted to automatically perform the inventive cleaning methodof FIG. 1. An exemplary IPA dryer that employs a fluid tank is disclosedin U.S. patent application Ser. No. 09/280,118, filed Mar. 26, 1999(AMAT No. 2894/CMP/RKK), the entirety of which is incorporated herein bythis reference.

[0034] The operation of both aspects of the IPA dryer 201 are describedbelow. In the first aspect, the hydrophobic wafer W is placed in thetank 203 whereby a layer of surfactant containing solution is formed onthe surfaces of the hydrophobic wafer W. The lifting mechanism 205elevates and lifts the hydrophobic wafer W from the fluid.

[0035] As the hydrophobic wafer W reaches the top of the tank fluid, therinsing fluid nozzles 207 are engaged and begin to spray pure DI waterto the layer of surfactant containing solution that has been formed onthe front and back surfaces of the hydrophobic wafer W, which creates anair/wafer/rinsing fluid interface in the form of a meniscus. As soon asthe hydrophobic wafer W intersects the pure DI water sprays from therinsing fluid nozzles 207, the drying vapor nozzles 211 are engaged anddirect a drying vapor flow to the rinsing fluid meniscus M which formson the surface of the hydrophobic wafer W. The drying vapors areabsorbed by the rinsing fluid, which lowers the surface tension of therinsing fluid and induces a Marangoni flow from the meniscus toward thebulk of the rinsing fluid. The Marangoni flow thereby dries thehydrophobic wafer W's surface. The wafer W may be lifted at a speedwhich does not result in the surfactant being completely rinsed from thewafer W (thereby avoiding direct contact between the DI water and thesurface of the wafer W) but that is slow enough to allow sufficient IPAdrying (e.g., 0.1 to 0.5 inches/sec.). Heated nitrogen may be directedto the hydrophobic wafer W's surfaces via a nozzle (not shown) tofurther aid the drying of the hydrophobic wafer W.

[0036] In the first aspect, because pure DI water is applied only to thelayer of diluted surfactant containing solution on the hydrophobic waferW's surface, and is not applied directly to the hydrophobic wafer W'ssurface, fewer water marks may form on the surfaces of the hydrophobicwafer W.

[0037] The operation of the second aspect may comprise the same steps asthe operation of the first aspect. In the operation of the secondaspect, however, the rinsing fluid nozzles 207 supply a dilutedsurfactant containing solution to the front and the back surfaces of thehydrophobic wafer W.

[0038] In the second aspect, because pure DI water is never used, andonly diluted surfactant containing solution is used to rinse thehydrophobic wafer W, water marks may not form on the surfaces thereof.

[0039]FIG. 4A is a partially sectional side view of an IPA dryer 301that employs an SRD 303 and that may rinse and dry a hydrophobic wafer Wusing the inventive cleaning method of FIG. 1. FIG. 4B is a top planview of the IPA dryer 301 of FIG. 4A.

[0040] Within the IPA dryer 301, the hydrophobic wafer W is shownsupported on a spin chuck 307. The spin chuck 307 is coupled to a motor309 adapted to rotate the spin chuck 307 about a vertical axis.

[0041] A supply comprising nozzles 311 a, 311 b is positioned to spray asurfactant containing solution and rinsing fluid, respectively acrossthe surface of the hydrophobic wafer W, and an organic solvent supplycomprising an IPA nozzle 313 (FIG. 4B) is positioned to flow IPA liquidacross the surface of the hydrophobic wafer W. In the first aspect, therinsing fluid may comprise pure DI water. In the second aspect, therinsing fluid may comprise a diluted surfactant containing solution.

[0042] The nozzles 311 a, 311 b and/or the IPA nozzle 313 are coupled toa controller 315, and the controller 315 comprises a memory having aprogram stored therein adapted to automatically perform the inventivecleaning method of FIG. 1.

[0043] The operation of both aspects of the IPA dryer 301 are describedbelow. In the first aspect, the nozzle 311 a supplies the surfactantcontaining solution to the surface of the hydrophobic wafer W, thusforming a layer of surfactant containing solution thereon while thechuck 307 rotates. Thereafter, the surfactant spray ceases and the spinchuck 307 continues to rotate at a slow speed (e.g., 300 rpm) while thenozzle 311 b sprays pure DI water to the layer of surfactant containingsolution formed on the surface of the hydrophobic wafer W. The DI waterspray continues for a short time (e.g., approximately five seconds orless). Then, the nozzle 311 b shuts off and the IPA nozzle 313 spraysIPA liquid to the surface of the hydrophobic wafer W. Each of thenozzles may begin in a position that sprays the center of the wafer andmay then scan radially across the wafer to the wafer's edge as the waferrotates.

[0044] The IPA liquid lowers the surface tension of the rinsing fluid,which allows the rinsing water to be easily removed from the surface ofthe hydrophobic wafer W. Thereafter, the motor 309 either maintains orincreases the rotational speed of the spin chuck 307 (e.g., toapproximately 1000 to 2500 rpm) such that any remaining DI water, IPAliquid, and surfactant containing solution is displaced from thehydrophobic wafer W via the rotational speed, and/or dried from thehydrophobic wafer W.

[0045] In the first aspect, because pure DI water is applied only to thelayer of surfactant containing solution formed on the hydrophobic waferW's surface, and is not applied directly to the hydrophobic wafer W'ssurface, fewer water marks may form on the surfaces of the hydrophobicwafer W. Also, as described above, the IPA liquid may rapidly remove thepure DI water from the surface of the hydrophobic wafer 305.

[0046] The second aspect may comprise the same steps as the firstaspect. In the second aspect, however, the nozzle 311 b supplies adiluted surfactant containing solution to the layer of surfactantcontaining solution on the surface of the hydrophobic wafer W (in oneaspect, for a short period of time, approximately ten seconds or less).Because pure DI water is never used, and only diluted surfactantcontaining solution is used to rinse the hydrophobic wafer W, watermarks may not form on the surfaces thereof.

[0047]FIG. 5 is a side view of an inventive scrubber 401 that mayperform the inventive cleaning method of FIG. 1. The inventive scrubber401 comprises a pair of PVA brushes 403 a, 403 b. Each brush maycomprise a plurality of raised nodules 405 across the surface thereof,and a plurality of valleys 407 located among the nodules 405. Theinventive scrubber 401 also may comprise a platform 409 adapted tosupport a hydrophobic wafer W and a mechanism (not shown) adapted torotate the pair of PVA brushes 403 a, 403 b. The platform 409 comprisesa plurality of spinning mechanisms 411 a-c adapted to spin thehydrophobic wafer W.

[0048] As further shown in FIG. 5, a plurality of spray nozzles 413coupled to a source of surfactant containing solution 415 are positionedto spray the surfactant containing solution at the surfaces of thehydrophobic wafer W during wafer scrubbing. A rinsing fluid nozzle 419is coupled to a source of rinsing fluid 421, and is positioned to sprayrinsing fluid at the surfaces of the hydrophobic wafer W either afterwafer scrubbing or during the final portion of wafer scrubbing when thebrushes are not in contact with the wafer. In the first aspect, thesource of rinsing fluid may comprise pure DI water. In the second aspectthe source of rinsing fluid 421 may comprise a diluted surfactantcontaining solution that is more dilute than the surfactant containingsolution contained in the source of surfactant containing solution 415.

[0049] A controller 423 is coupled to both sources 415, 421, andcontains a program 425 adapted to control the supply of surfactantcontaining solution and the supply of rinsing fluid delivered to thesurfaces of the hydrophobic wafer W. The controller 423 may also becoupled to the pair of PVA brushes 403 a, 403 b. The program 425controls the scrubber 401 so as to operate as described below. Theinventive scrubber 401 may be configured as described in U.S. patentapplication Ser. No. 09/191,061, filed Nov. 11, 1998 titled “METHOD ANDAPPARATUS FOR CLEANING THE EDGE OF A THIN DISC”, the entire disclosureof which is incorporated herein by this reference.

[0050] The operation of both aspects of the inventive scrubber 401 aredescribed below. In the first aspect, the PVA brushes 403 a, 403 b areinitially in an open position (not shown), a sufficient distance fromeach other so as to allow a hydrophobic wafer W to be insertedtherebetween. Thereafter, the hydrophobic wafer W to be cleaned ispositioned between the PVA brushes 403 a, 403 b and the brushes assume aclosed position, sufficiently close to each other so as to both hold thehydrophobic wafer W in place therebetween and to exert a force on thewafer surfaces sufficient to achieve effective cleaning. Mechanisms (notshown) adapted to move the brushes 403 a, 403 b between the open andclosed positions are well known in the art and are therefore not furtherdescribed herein.

[0051] Once the brushes 403 a, 403 b are in the closed position, aspinning mechanism (not shown) is engaged and the brushes 403 a, 403 bbegin to spin. In one aspect, the brushes 403 a, 403 b spin in oppositedirections applying forces to the hydrophobic wafer W in a firstdirection (e.g., into the page) while the hydrophobic wafer W is rotatedeither clockwise or counterclockwise via the spinning mechanisms 411a-c.

[0052] The front and back surfaces of the wafer W are cleaned of slurryresidue or other particles when contacted by the nodules 405 of thebrushes 403 a, 403 b, respectively. As the brushes 403 a, 403 b rotate,the hydrophobic wafer W is cleaned with the surfactant containingsolution, which is sprayed on the front and back surfaces of thehydrophobic wafer W via the spray nozzles 413, thus forming a layer ofsurfactant containing solution thereon. After the hydrophobic wafer W issufficiently scrubbed, the brushes 403 a, 405 b may assume the openposition while the spinning mechanism continues to rotate thehydrophobic wafer W at a slow speed (e.g., 50 rpm). The rinsing fluidnozzle 419 sprays pure DI water for a short period of time (e.g.,approximately five seconds or less) to the layer of surfactantcontaining solution formed on the front and back surfaces of thehydrophobic wafer W. After the rinsing step, hot nitrogen gas may bedirected onto the wafer surfaces to dry the hydrophobic wafer W whilethe wafer W rotates. Alternatively a rinsing fluid nozzle and an IPAnozzle may scan radially from the center to the edge of the wafer, asthe wafer rotates. Because pure DI water is applied only to the layer ofsurfactant containing solution on the hydrophobic wafer W's surface, andis not applied directly to the hydrophobic wafer W's surface, fewerwater marks may form on the surfaces of the hydrophobic wafer W.

[0053] The second aspect of operation may comprise the same steps as thefirst aspect of operation. In the second aspect, however, the rinsingfluid nozzle 419 supplies a diluted surfactant containing solution tothe front and the back surfaces of the hydrophobic wafer W (in oneaspect, for a short period of time, such as approximately ten seconds orless).

[0054] In the second aspect, because pure DI water is never used, andonly diluted surfactant containing solution is used to rinse thehydrophobic wafer W, water marks may not form on the surfaces thereof.

[0055] As previously stated, other aspects of the invention comprise acleaning sequence that is performed within a plurality of apparatuses,as described with reference to FIGS. 6 and 7.

[0056]FIG. 6 is a flowchart of an inventive cleaning method 501 that maybe performed in any conventional cleaning system. The inventive cleaningmethod 501 starts at step 503.

[0057] In step 505, a surfactant containing solution is applied to thesurfaces of a hydrophobic wafer in a first cleaning apparatus so as toform a layer of surfactant containing solution thereon, which helps acleaning solution wet the hydrophobic wafer's surfaces as describedfurther below. The surfactant molecules may comprise a hydrophilic headportion and a hydrophobic tail portion. The hydrophobic portion mayattach the surfactant molecule to the hydrophobic surface of the wafer.The hydrophilic end may attach to the cleaning solution, which enables acleaning solution to wet the hydrophobic surface of the wafer. Forexample, the first cleaning apparatus may comprise a megasonic cleaneras described below with reference to FIG. 6 and/or the inventivescrubber 401 as described above with reference to FIG. 4, etc.

[0058] Then, the hydrophobic wafer having the layer of surfactantcontaining solution thereon is transferred to a second cleaningapparatus in step 507. The transfer occurs quickly enough so that thehydrophobic wafer maintains the layer of surfactant containing solutionthereon as it transfers to the second cleaning apparatus. Because thelayer of the surfactant containing solution that has formed on thehydrophobic wafer's surfaces may dry more slowly than pure DI water (andbecause the transfer occurs sufficiently quick) the hydrophobic wafer'ssurfaces remain wet as the wafer is transferred from the first cleaningapparatus to the second cleaning apparatus, which may reduce theaffinity of particle contaminants to the hydrophobic surfaces.

[0059] The second cleaning apparatus may comprise the SRD 101 asdescribed above with reference to FIG. 2, the IPA dryer 201 as describedabove with reference to FIG. 3, the IPA dryer 301 as described abovewith reference to FIG. 4, the inventive scrubber 401 as described abovewith reference to FIG. 5, or any rinsing and drying apparatus that mayrinse and dry a wafer in accordance with the method of FIG. 1.

[0060] In step 509 a, 509 b, in the second cleaning apparatus, a rinsingfluid is applied to the surface of the hydrophobic wafer, having thelayer of surfactant containing solution formed thereon, for a shorttime. In a first aspect (step 509 a) the rinsing fluid is DI water andis applied for a sufficiently short period of time such that as thelayer of surfactant containing solution formed on the hydrophobicwafer's surface is removed or nearly removed, the DI water spray stops.Accordingly, DI water is not applied directly to the hydrophobic wafer'ssurface. Test results show that a DI water rinse applied with 15-20 psiat a flow rate of 500 ml/minute will either remove or will nearly haveremoved a surfactant layer from a 300 mm wafer after a short time (e.g.,approximately five seconds).

[0061] In a second aspect (step 509 b), a diluted surfactant containingsolution that is more dilute than the surfactant containing solutionused in step 505 is applied to the wafer W. The dilution of thesurfactant containing solution may increase over time.

[0062] Thereafter, in step 511, while still in the second cleaningapparatus, the hydrophobic wafer is dried (e.g., by spinning or throughapplication of IPA, as described with reference to FIGS. 3-4B). In step513 the inventive process ends.

[0063]FIG. 7 is a schematic side elevational view of an integratedcleaner 601 (e.g., having a mechanism for transferring wafers directlyfrom one cleaning apparatus to the next) that may employ the inventivecleaning method 501 of FIG. 6. After a hydrophobic wafer W is polishedby a polisher (not shown), the hydrophobic wafer W may enter the cleaner601 to be cleaned and dried. The cleaner 601 may comprise a plurality ofcleaning modules 603, each cleaning module 603 having a wafer support605 a-d that may support a vertically oriented wafer W. The cleaningmodules 603 may include a megasonic cleaner module 607, a pair ofscrubber modules 609 a-b, and a spin-rinse-dryer module 611. The cleaner601 also may optionally comprise an input module 613 and an outputmodule 615. Both the input module 613 and the output module 615 may havea wafer support 605 e, 605 f, respectively, that supports a wafer in ahorizontal orientation.

[0064] A wafer transfer mechanism 617, having a plurality of waferhandlers 619 a-e, may be movably coupled above the modules 607-615. Thewafer handlers 619 a-e may be positioned to selectively place andextract a wafer to and from the wafer supports 605 a-f upon actuation ofthe wafer transfer mechanism 617. The wafer transfer mechanism 617 maybe adapted to lift, lower, and to index horizontally forward andbackward so as to transfer wafers between the input module 613, thecleaning modules 603, and the output module 615. Specifically, the wafertransfer mechanism 617 may comprise an overhead walking beam-type robot,and the cleaner 601 may be configured as described in U.S. patentapplication Ser. No. 09/558,815, filed Apr. 26, 2000 titled“SEMICONDUCTOR SUBSTRATE CLEANING SYSTEM” the entire disclosure of whichis incorporated herein by this reference.

[0065] In operation, a horizontally oriented hydrophobic wafer W may beloaded onto the wafer support 605 e of the input module 613. Whilere-orienting the wafer W, the first wafer handler 619 a may elevate uponactuation of the wafer transfer mechanism 617, thereby extracting thewafer W from the input module 613, and may index (i.e., movehorizontally) to position the wafer W above the megasonic cleaner module607. Thereafter, the first wafer handler 619 a may lower the verticallyoriented wafer W into the megasonic cleaner module 607 and may place thewafer W on the wafer support 605 a. The wafer W may then bemegasonically cleaned with a surfactant containing solution bath.

[0066] After the vertically oriented wafer W is megasonically cleaned inthe surfactant containing solution bath, the second wafer handler 619 bmay extract the wafer W and quickly transfer the wafer W to the firstscrubber module 609 a for scrubbing. Thereafter, the third substratehandler 619 c may quickly transfer the wafer W to the second scrubbermodule 609 b for scrubbing. Within the scrubber modules 609 a-b, asurfactant containing solution may be applied to the wafer W while thescrubber brushes scrub the surface of the wafer W.

[0067] After cleaning within the scrubber modules 609 a-b is complete,the fourth substrate handler 619 d may extract the wafer W, having thelayer of surfactant containing solution thereon, and may transfer thewafer W to the spin-rinse-dryer module 611. Within the spin-rinse-dryermodule 611, the wafer W may be rotated at high speed (e.g., 900 RPM)while either pure DI water (for a short period of time only) or adiluted surfactant containing solution is sprayed on the layer ofsurfactant containing solution that is formed on the wafer W. After thewafer W is sufficiently rinsed (as described above with reference toFIG. 1), the wafer W is spin-dried.

[0068] The fifth wafer handler 619 e may then extract the verticallyoriented wafer W from the spin-rinse-dryer module 611, horizontallyorient the wafer W, and place the wafer W on the horizontal wafersupport 605 f of the output module 615. Thereafter, the wafer W may beextracted from the cleaner 601 by a wafer handler.

[0069] Because throughout the cleaning an drying process, the solutionsthat directly touch the surfaces of the hydrophobic wafer W aresurfactant containing solutions, the hydrophobic wafer W may beeffectively cleaned, rinsed, and dried with minimal water marks.

[0070] The foregoing description discloses only the preferredembodiments of the invention, modifications of the above-disclosedapparatus and method which fall within the scope of the invention willbe readily apparent to those of ordinary skill in the art. For instance,the invention can be performed within any conventional scrubber (whetheremploying one or more roller brushes or one or more disk shaped brushesand/or any conventional spin rinse dryer or IPA dryer can be adapted toperform the present invention. Although a vertical orientation may beemployed, the invention may also be performed on wafers having otherorientations (e.g. horizontal). Also, when more dilute surfactant isemployed as the rinsing fluid, the surfactant concentration maygradually decrease over time. In fact, in a further aspect, theinvention may comprise applying a surfactant containing solution to ahydrophobic wafer and thereafter drying the hydrophobic wafer, withoutapplying pure DI water. Accordingly, the step of applying a first moreconcentrated surfactant containing solution may be omitted. In anexemplary aspect, a WAKO NCW surfactant containing solution containingless than 500 ppm surfactant may be applied to a hydrophobic wafer (e.g.in any apparatus or apparatuses capable of rinsing and drying a wafer)and the wafer thereafter be dried, without applying pure DI water to thewafer.

[0071] Finally, it will be understood that as used herein wafer is notto be limited to a patterned or unpatterned semiconductor substrate butmay include glass substrates, flat panel displays and the like. Also, asused herein pure DI water means deionized water that is not mixed withanother substance. Thus pure DI water does not include DI water that ismixed or combined with a surfactant (whether mixed or combined prior tobeing applied to the wafer, or mixed or combined on the wafer'ssurface).

[0072] Accordingly, while the present invention has been disclosed inconnection with the preferred embodiments thereof, it should beunderstood that other embodiments may fall within the spirit and scopeof the invention, as defined by the following claims.

The invention claimed is:
 1. A method of cleaning a hydrophobic wafer,comprising: applying a surfactant containing solution to a surface of ahydrophobic wafer in a first cleaning apparatus to thereby form a layerof surfactant on the surface of the hydrophobic wafer; transferring thehydrophobic wafer having the surfactant layer formed thereon to a secondcleaning apparatus; rinsing the surface of a hydrophobic wafer with pureDI water in the second cleaning apparatus; and drying the hydrophobicwafer in the second cleaning apparatus; wherein pure DI water is appliedto the hydrophobic wafer only in the rinsing step and whereintransferring the hydrophobic wafer to a second cleaning apparatuscomprises maintaining a layer of surfactant containing solution on thehydrophobic wafer as the hydrophobic wafer transfers to a secondcleaning apparatus.
 2. The method of claim 1 wherein applying asurfactant containing solution to a surface of a hydrophobic wafer in afirst cleaning apparatus comprises at least partially submerging thehydrophobic wafer in a tank of fluid that contains a surfactantcontaining solution.
 3. The method of claim 1 wherein applying asurfactant containing solution to a surface of a hydrophobic wafer in afirst cleaning apparatus comprising scrubbing the hydrophobic waferusing the surfactant containing solution in a first scrubber.
 4. Themethod of claim 1 wherein transferring the hydrophobic wafer to a secondcleaning apparatus comprises transferring the hydrophobic wafer to ascrubber.
 5. The method of claim 1 wherein transferring the hydrophobicwafer to a second cleaning apparatus comprises transferring thehydrophobic wafer to a spin-rinse-dryer.
 6. The method of claim 1wherein the surfactant containing solution comprises a WAKO NCWsurfactant.
 7. The method of claim 6 wherein the WAKO NCW surfactantcomprises a concentration of 0.01% to 0.1% by volume.
 8. The method ofclaim 1 wherein rinsing the surface of a hydrophobic wafer with pure DIwater in a second cleaning apparatus comprises rinsing the surface of ahydrophobic wafer with pure DI water in a second cleaning apparatus for5 seconds or less.
 9. The method of claim 1 wherein transferring thehydrophobic wafer to a second cleaning apparatus comprises transferringthe hydrophobic wafer to an IPA dryer.
 10. The method of claim 1 whereindrying the hydrophobic wafer comprises Marangoni drying the hydrophobicwafer.
 11. A method of rinsing and drying a hydrophobic wafer,comprising: placing a hydrophobic wafer in a cleaning apparatus;applying a diluted surfactant to the surface of the hydrophobic waferwithin the cleaning apparatus; and drying the hydrophobic wafer withinthe cleaning apparatus.
 12. The method of claim 11 wherein the dilutedsurfactant containing solution comprises a concentration of 0.01% to0.1% surfactant by volume.
 13. The method of claim 11 wherein thediluted surfactant is applied for five seconds or less.
 14. The methodof claim 11 wherein placing a hydrophobic wafer in a cleaning apparatuscomprises placing the hydrophobic wafer in a spin-rinse-dryer.
 15. Themethod of claim 11 wherein placing a hydrophobic wafer in a cleaningapparatus comprises placing the hydrophobic wafer in a scrubber.
 16. Themethod of claim 11 wherein placing a hydrophobic wafer in a cleaningapparatus comprises placing the hydrophobic wafer in a Marangoni dryerand wherein drying the hydrophobic wafer comprises Marangoni drying. 17.The method of claim 16 wherein the Marangoni dryer comprises a tankcontaining a surfactant.
 18. The method of claim 16 wherein theMarangoni dryer comprises a spin-rinse-dryer.
 19. A method of rinsingand drying a hydrophobic wafer, comprising: placing a hydrophobic waferin a cleaning apparatus; applying a surfactant to the surface of thehydrophobic wafer to form a surfactant layer thereon; spraying puredeionized water on the surface of the hydrophobic wafer; ceasing thedeionized water spray as soon as the surfactant layer is rinsed from thesurface of the hydrophobic wafer; and drying the hydrophobic wafer. 20.The method of claim 19 wherein placing a hydrophobic wafer in a cleaningapparatus comprises placing the hydrophobic wafer in a spin-rinse-dryer.21. The method of claim 19 wherein placing a hydrophobic wafer in acleaning apparatus comprises placing the hydrophobic wafer in ascrubber.
 22. The method of claim 19 wherein placing a hydrophobic waferin a cleaning apparatus comprises placing the hydrophobic wafer in aMarangoni dryer and wherein drying the hydrophobic wafer comprisesMarangoni drying.
 23. A method of rinsing and drying a hydrophobicwafer, comprising: placing a hydrophobic wafer in a cleaning apparatus;applying a surfactant to the surface of the hydrophobic wafer to form asurfactant layer thereon; spraying pure deionized water on the surfaceof the hydrophobic wafer; ceasing the deionized water spray within fiveseconds; and drying the hydrophobic wafer.
 24. The method of claim 23wherein placing a hydrophobic wafer in a cleaning apparatus comprisesplacing the hydrophobic wafer in a spin-rinse-dryer.
 25. The method ofclaim 23 wherein placing a hydrophobic wafer in a cleaning apparatuscomprises placing the hydrophobic wafer in a scrubber.
 26. The method ofclaim 23 wherein placing a hydrophobic wafer in a cleaning apparatuscomprises placing the hydrophobic wafer in a Marangoni dryer and whereindrying the hydrophobic wafer comprises Marangoni drying.
 27. A method ofrinsing and drying a hydrophobic wafer, comprising: placing ahydrophobic wafer in a cleaning apparatus; applying a surfactant to thesurface of the hydrophobic wafer to form a surfactant layer thereon;spraying pure deionized water on the surface of the hydrophobic wafer;ceasing the deionized water spray before the surfactant layer iscompletely rinsed from the surface of the hydrophobic wafer; and dryingthe hydrophobic wafer.
 28. The method of claim 27 wherein placing ahydrophobic wafer in a cleaning apparatus comprises placing thehydrophobic wafer in a spin-rinse-dryer.
 29. The method of claim 27wherein placing a hydrophobic wafer in a cleaning apparatus comprisesplacing the hydrophobic wafer in a scrubber.
 30. The method of claim 27wherein placing a hydrophobic wafer in a cleaning apparatus comprisesplacing the hydrophobic wafer in a Marangoni dryer and wherein dryingthe hydrophobic wafer comprises Marangoni drying.